Hydraulic lift system for wheel stretchers



July 16, 1968 E. L. WILLIAMS 3,393,004

HYDRAULIC LIFT SYSTEM FOR WHEEL STRETCHERS Filed Oct. 6, 1966 3 Sheets-Sheet 1 i553 -4 Is 41 M an.

July 16, 1968 E. L. WILLIAMS 3,393,004

HYDRAULIC LIFT SYSTEM FOR WHEEL STRETCHERS Filed Oct. 6, 1966 3 Sheets-Sheet 2 I I 42 9b 54 1 it '3 9o 15 J 88 -a so k l u a l I '25 28 ii! 7 l v iii' 24 l WIIIIIIIIII A\ f i INVENTOR.

51/24 Zia/104w Mz/AMS 6 i ATTORNEYS July 1 6, 1968 3 E. L. WILLIAMS 3,393,004

HYDRAULIC Lil-"T SYSTEM FOR WHEEL STRETCHERS Filed Oct. 6, 1966 3 Sheets-Sheet 5 g avsfit I N VENTOR. 5424 Zia/V420 MAM/V5 5) I-YTT ORNEYS United States Patent 1 3,393,004 HYDRAULIC LIFT SYSTEM FOR WHEEL STRETCHERS Earl Leonard Williams, Medina, Ohio, assignor to Simmons Company, New York, N.Y., a corporation of Delaware Filed Oct. 6, 1966, Ser. No. 584,755 2 Claims. (Cl. 296-20) This invention is concerned with the adjustability of wheel stretchers in which the patient-supporting platform can be raised and lowered, and tilted from end to end.

A wheel stretcher is basically a vehicle for transporting a human body, usually supine, from an examining table to an operating table, andto and from a bed. To minimize the incidence of injury, it is desirable that the patient-supporting surface of the stretcher be adjustable in height to match the non-uniform heights of the surfaces to or from which the patients body is transferred. Moreover, because such transfers and transportation may need to be. accomplished under emergency conditions, and indeed the stretcher at times required to perform the function of examining table and operating table as well as transport vehicle, it is desirable that such tables also be tiltable endwise in order to put the supine body in either head-down or foot-down position during examination, emergency treatment, or transport.

Stretchers which accomplish these movements are already known.

This invention is concerned rather with an improved height-adjusting mechanism for accomplishing the foregoing adjustments in a very flexible manner by means of a hydraulic mechanism which makes it possible directly to tilt the patient-supporting platform toward either end, irrespective of whether the platform was initially raised, lowered, or at some intermediate position, so that the patient can be put immediately into head-up or head-down position without regard for his orientation on the patientsupporting surface. Stated another way, either end of the stretcher can serve equally as the head-end or foot-end, and a body reposed thereon can be put without delay into the shock or drainage position.

Basically, this flexibility is accomplished by supporting the patient-supporting platform pivotally at two longitudinally spaced points which can be raised or lowered independently or simultaneously by hydraulic lift cylinders, each of which is provided with its own pump. The two pumps are connected together for operation in unison, but the output of either may be bypassed to the reservoir without effect upon the lift cylinder by separate manuallyoperated valves which also permit the associated lift cylinder to retract, and the end of the table associated therewith to lower itself by gravity.

The invention will be better understood by reference to the accompanying drawings in which:

FIGURE 1 is an isometric view of a stretcher in accordance with the invention, partially broken away to show certain details of construction which would not otherwise be apparent in FIGURE 1, and showing by means of broken-line positions some of the aforementioned movement of which the patient-supporting platform is capable;

FIGURE 2 is a similarly oriented isometric view, more or less schematic, showing the placement of the hydraulic circuitry in relation to the stretcher as seen in FIGURE 1;

FIGURE 3 is a sectional view taken on the line 3-3 of FIGURE 1 to illustrate the construction of the telescopic columns which support the patient-supporting surface, as well as the hydraulic lift cylinders therein, and the attachment of the column to the underside of the patient-supporting surface and to the undercarriage;

FIGURE 4 is a sectional elevational view through one of the dual pumps, taken on the line 4-4 of FIGURE 2; and

3,393,004 Patented July 16, 1968 ICC FIGURE 5 is a sectional view of the aforementioned manually-operated bypass valves, taken along the line 55 of FIGURE 2.

As seen particularly in FIGURE 1, the stretcher has an undercarriage 10 which is horizontal and basically planar, and provided near each of its four corners with castering wheels of generous diametenThe undercarriage may be a weldment of tubes or other structural shapes covered with sheet metal but the details of its construction are unimportant.

A patient-supporting platform 12 is supported by two longitudinally-spaced telescopic columns 14 and 15 mounted on the undercarriage along its centerline. A sheet metal cover 16, which merely conceals the hydraulics, appears in FIGURE 1 to unite the two columns into a single elongate central pedestal.

One of the columns 14 is secured to the underside of the patient-Supporting platform in a simple pivotal connection 18 whose axis extends transversely of the stretcher, and the other column 15 is secured to the underside of the patient-supporting platform in a connection 20 which is similarly pivotal, but which by means of a longitudinal slot 22 in the underframing of the patient-supporting platform also accommodates the endwise sliding movement which accompanies the placement of the patient-supportin g platform in its tilted positions.

Also as seen in FIGURE 1, the patient-supporting platform 12 is basically a planar frame, which may also be a weldment of tubes or other structural shapes preferably covered with sheet metal and a cushion. The platform is secured, as indicated in FIGURE 1, to a wide, shallow, inverted channel member 24 which extends longitudinally and centrally of the patient-supporting platform, and provides the points of connection of the platform to the supporting columns.

The supporting column 15, which is the more remote in FIGURE 1, is sectioned in FIGURE 3, from which its detail will be evident. It comprises a cast base 26 which is secured, as by a suitable bolting flange, to the undercarriage 10. Screwed to the base 26 is an upstanding metal tube 28 having at its upper end a number, preferably four, of internally-threaded bosses 30 which position bearing plugs 32 of nylon or Teflon plastic or the like for engagement with the outer surface of the smaller-diameter, telescoped, upper tube 34 of the column. At its lower end the upper tube 34 is provided with similar bosses 30 and bearing plugs 32' which, together with those of the lower tube, form the slide bearings for the telescopic movement of the column.

Concentrically within each column is a hydraulic lift cylinder or jack 36 which consists of an outer shell 38 threaded into the cast base 26 of the column, and an interior piston 40 having a customary seal with the cylinder wall and a connecting rod 42 extending upwardly therefrom. The upper end of the connecting rod is held by means of a set screw 44 in a socket in the bottom of a crossplate 46 secured diametrically in the upper end of the upper tube 34, and transversely of the stretcher, by means of screws 48. A tubular socket 50 in the upper edge of the crossplate 46 fits comfortably between the flanges 52 of channel member 24 on the underside of the patientsupporting platform and receives a shaft 54 which passes through the flanges 52, to which it is assembled with washers 56 and suitable keys 58. As earlier indicated in reference to FIGURE 1, the crossplate of the column 15 is secured to the channel member in a slotted pivotal connection which permits endwise movement of the patient-supporting platform relative to the one column, in addition to its pivotal movement relative to both columns, when the patient-supporting platform is moved diagonally.

Feeding into the base plate 26 of the column is a line 3 60 which is connected through a bored channel 62 to the interior of the lift cylinder.

The piston 40 is provided with a normally closed relief valve 74 which is illustrated in FIGURE 3 in the open position. The valve comprises an inverted conical seat 76 at the bored lower end of the connecting rod 42, and a ball check 78 which is urged upwardly toward the seat by a light compression spring 80 supported on its underside by a cap 82 screwed to the lower end of the connecting rod. The cap 82 also serves to maintain the assembly of the'piston with the connecting rod, andthrough an open center channel 84 provides communication to the relief valve 74 from the interior of the cylinder.

Extendingly upwardly through the bore in the lower end of the connecting rod is a plunger 86 of smaller diameter than the central bore in the connecting rod, the plunger having at its upper end a cross bar 88 which emerges from the connecting rod through larger holes 90 drilled in the walls of the bore. The cross bar has a length slightly less of the inner diameter of the cylinder, and when the piston is near its position of extreme elevation, the cross bar abuts the underside of a collar pressed in the very upper end of the cylinder. A slight further upward movement of the piston results in a relatively downward movement of the plunger 86 therein, thus unseating the ball check 78 and providing an open passage from the interior of the cylinder, through the check and central bore of the connecting rod to the upper side of the piston and thence outward through a line 92 to the reservoir. The upper end of the cylinder 36 is closed with a cap 94 having a packing gland 96 through which the connecting rod emerges, and which is sufficient to contain such minor pressure as may be built up above the piston by the throttling effect of the return line to the reservoir in the face of continued delivery by the pump to the lift cylinder when the piston of the lift cylinder is at the extreme upper end of its stroke.

In FIGURE 2,, the columns and sheet metal covers are omitted to better illustrate the hydraulic circuitry, and the bases 26 of the cylinders 36 arfe represented diagrammatically as blocks. A simple can reservoir 98, vented to atmosphere at its top, is placed in line between the two lift cylinders 36, and more or less adjacent to the dual pumps 100 which are also placed in line with and between the cylinders 36 so that the entire assembly can be conveniently shrouded by the sheet metal cover 16 for clean design, as indicated in FIGURE 1.

The pumps 100 (see FIG. 4) are two simple piston pumps mounted side-by-side on a common base 102 into which the cylinders 104 are screwed vertically. The piston rods 106 of the two pumps are connected together by a yoke 108 at their upper ends, and the pistons are normally drawn to their upper positions by a tension spring 110 connected between the yoke 108 and the surmounted cross bar 112 of a frame 114 secured to the pump base.

The pistons are thrust downwardly by a pedal-operated linkage (FIG. 2) which consists of a lever 116 pivoted to the undercarriage on its underside and having at one end a foldable pedal 118 which extends longitudinally outwardly from the undercarriage. At its other end it is connected by means of a thrust link 120 to dual walking beams 122, the opposite ends of which are connected to the upper ends of the piston rods 106, and confined near their mid-points by rocking fulcrums 124 on links 126 connected to the pump base. Thus it will be apparent that by a downward force on the pedal 118, the pistons are thrust downward in their respective cylinders.

In the common base block 102 of the dual pumps is bored a separate through-channel 128 for each of the pumps, each such channel communicating directly with the pump cylinder, with the reservoir through a line 130 and ball check 132, and with the lift cylinder through a line 134 and ball check 136, it being apparent from FIGURE 4 that the ball check 132 in the line from the reservoir closes on the power stroke (down) of the piston, and that the ball check 136 in line to the lift cylinder seats on the intakestroke (up) of the pump pistoziJ As seen in FIGURE 2, the delivery lines 60-134 and 60134 from the pumps to their respective lift cylinders are broken with T-connectors.138 and 138 and led upwardly by lines 140. and 140' to the manually operated bypass valves 142 and 142 carried. at one end of the patient-supporting platform 12 above the pump-operating pedal 118, as shown in FIGURES l and 2, thervalves-bzing connected to a common returnline 152 to the reservoir 38. 1

FIGURE 5 shows the valve 142 in section, its companion 142 having identical construction. Each comprises a housing 144 having threaded inlet a'n'doutlet passages 146 and 148 which receive the coupling members by means of which the valves are connected to the lines140 and 140, and to the return line 152. In each-housing 144 is a barrier wall 154 having an aperture 155-, with conical walls to receive a conical meterin stop or needle 156. The stop is normally seated by the pressure of springs (not shown) in the barrel 157 associated with the housing 144, and is operable against that spring pressure by a rock lever 158 which is pinned to the stern of the stop 156 and has a cam surface bearing on the face of the barrel 157. It will be apparent from FIGURES l, 2 and 5 that finger pressure upward on the lever 158 opens the valve, and. that the degree of movement of the lever governs the amount of the opening, i.e. meters the flow. A guard frame 159 shields the valve levers from unintended operation.

Accordingly, when the valve 142' is opened, gravity forces the piston of the associated lift-cylinder down, at a rate controlled by the operators manipulation of the control lever. If the pump be operating while the .valve 142' is open, it delivers directly to the reservoir under substantially no load other than the throttling effect of the bypass path.

By referring to FIGURES 1 and 2, it will be seen that the tilting attitudes .of the patient-supporting platform necessitate some flexibility in the hydraulic connections to the manually operated valves. This ,is accomplished by grouping the lines 140, 140', and 152, to and from the valves 142-142, in a common downwardlyextending orientation mid-way between the pivotal connections of the patient-supporting platform to the telescopic columns, and by providing intermediate flexible hose connections, indicated diagrammatically at 160, in the lines 140, 140' and 152 at that location.

It will be appreciated that with the foregoinghydraulic arrangement, in which the lift cylinder of each column is provided with its separate pump, there can be no preference of one lift cylinder over the other as a result of unequally distributed load, as is the case when a single pump supplies multiple lift cylinders. In the arrangement of this invention, each pump delivers independently on every application of pumping power. If the patient-supporting platform should be tilted at the commencement of any pumping operation, it is obvious therefore that in the absence of any manipulation of the hand-operated bypass valves, the patient-supporting platform will proceed upwardly in the tilted condition until the more; extended liftcylinder reaches its upper extremity, whereupomcontim ued pressure delivery to that lift cylinder is automatically bypassed through the relief valve at the top of the cylinder until both cylinders are .fully. extended and the patient platform is level. Continued pumping thereafter simply bypasses hydraulic fluid through the relief valves at the top of each lift cylinder.

From the uppermost position either or both ends of the patient-supporting surface can be loweredsimply by depressing the valve operating levers at the end-of the patient-supporting platform. This opensthe lif-t cylinder, through the valve, to the common return line to,,th e reservoir. I 1 I It will also be apparent that thepumping effect of either pump may be nullified while the pumps are in operation by opening its associated bypass valve, which permits the patient-supporting surface to be elevated at one end while the opposite end, if raised, will be lowered either sequentially or simultaneously, depending upon the load and upon the metering adjustment made by the operation of the valve controlling the lift cylinders at that end.

By providing a separate pump for each of the lifting columns and separate control for the bypassing thereof, I have greatly increased the flexibility of operation of wheel stretchers, as well as providing for the immediate placement of the patient-supporting surface at any position of tilt within its operating limits, all under the positive control of a single attendant and without regard for the orientation in which the patient was initially deposited on the supporting platform.

What is claimed is:

1. For use in a wheeled stretcher havin a wheeled undercarriage, a patient-supporting platform, and two longitudinally-spaced adjustable-height supports on said undercarriage each having at its upper end a pivotal connection with the platform on an axis extending transversely of the platform:

an improved lift mechanism which permits the direct placement of the patient-supporting platform in endwise tilt in either direction from any previous position;

the improved lift mechanism comprising 1) a hydraulic lift cylinder for adjusting each support,

(2) a separate positive-displacement pump connected to each such cylinder,

(3) means for operating the pumps in unison,

(4) a reservoir from which the pumps draw,

(5) a relief valve opening automatically from each cylinder to the reservoir when the cylinder reaches a predetermined extension, and

(6) a separate hand-operated normally-closed valve in fluid communication with each cylinder and the reservoir to vent its associated cylinder to the reservoir.

2. The structure of claim 1 in which the pumps are piston pumps mounted on the undercarriage, the means for operating the pumps in unison is a pedal-operated linkage with spring return and common connection to the pump pistons, and the hand-operated valves are located on the platform and above the pedal, thus to accommodate the operation of the platform to a single attendant.

References Cited UNITED STATES PATENTS PHILIP GOODMAN, Primary Examiner. 

1. FOR USE IN A WHEELED STRETCHER HAVING A WHEELED UNDERCARRIAGE, A PATIENT-SUPPORTING PLATFORM, AND TWO LONGITUDINALLY-SPACED ADJUSTABLE-HEIGHT SUPPORTS ON SAID UNDERCARRIAGE EACH HAVING AT ITS UPPER END A PIVOTAL CONNECTION WITH THE PLATFORM ON AN AXIS EXTENDING TRANSVERSELY OF THE PLATFORM: AN IMPROVED LIFT MECHANISM WHICH PERMITS THE DIRECT PLACEMENT OF THE PATIENT-SUPPORTING PLATFORM IN ENDWISE TILT IN EITHER DIRECTION FROM ANY PREVIOUS POSITION; THE IMPROVED LIFT MECHANISM COMPRISING (1) A HYDRAULIC LIFT CLYINDER FOR ADJUSTING EACH SUPPORT, (2) A SEPARATE POSITIVE-DISPLACEMENT PUMP CONNECTED TO EACH SUCH CYLINDER, (3) MEANS FOR OPERATING THE PUMPS IN UNISON, (4) A RESERVOIR FROM WHICH THE PUMPS DRAW, (5) A RELIEF VALVE OPENING AUTOMATICALLY FROM EACH CYLINDER TO THE RESERVOIR WHEN THE CYLINDER REACHES A PREDETERMINED EXTENSION, AND (6) A SEPARATE HAND-OPERATED NORMALLY-CLOSED VALVE IN FLUID COMMUNICATION WITH EACH CYLINDER AND THE RESERVOIR TO VENT ITS ASSOCIATED CYLINDER TO THE RESERVOIR. 